1. Field of the Invention
The invention relates to an apparatus for the continuous measurement of the mass of a continuously conveyed sliver for the purpose of evening up the sliver.
2. Description of Background and Other Information
In the field of spinning processes, it is the function of the drawing device of a drafting frame, for example, to "even up" a sliver before manufacturing a roving yarn from such a prepared sliver. The evening up takes place by the doubling of several slivers and by changing or regulating the speed of the rollers conveying the slivers in a drafting area of the drawing device of a drafting frame, or by changing the speed of feed rollers at the entrance of a carding machine which produces slivers. If the mass of a continuously conveyed sliver either exceeds or falls below a predetermined value, such deviations are compensated for by changes in the conveyance speed for providing either more or less drafting for the evening up.
The changes in the conveyance speed are made by means of a measuring apparatus and a control device cooperating with the measuring apparatus, whereby the control device is provided for effecting appropriate changes in the speed of the roller drives. To this effect, the sliver is compressed in the measuring apparatus to a predetermined extent and the thickness of the thus formed volume is measured, whereby deviations from a predetermined desired thickness, identifying the evening up, generate signals for the control devices.
A measuring apparatus having the above-mentioned function is known which, with regard to its axle bearings, consists of a stationary driving roller and a movable carrier roller which, between them, form a roller slit which is variable with regard to its dimension. The driven driving roller and the carrier roller, which is driven by way of friction, are both arranged as step rollers which are both engaged in such a manner that a roller slit is formed in the direction of the sliver's movement, which is open in the direction of movement, but is otherwise limited by the rollers' circumferences and the steps, whereby the sliver is compressed for the purpose of measuring the thickness of the sliver when the sliver passes between the rollers.
The carrier roller's axle bearings are provided by means of leaf springs attached to an anchoring in such a manner that the axle bearings may perform parallel movements. Furthermore, springs act upon the axle bearings of the carrier roller, the forces of which are adjusted such that the carrier roller is pressed onto the driving roller with a predetermined pressure. In the event of changes in the compressed sliver volume caused by an accumulation of mass, the roller slit either extends or closes under a pendulum displacement of the axle position of the carrier roller, whereby the amount of the pendulum displacement is monitored by a sensor for generating control signals.
The known apparatus constitutes an oscillating body in which natural oscillations, which are subsidingly dampened in operation, superimpose with excitation oscillations caused by the movements of the carrier rollers. Due to the construction of this arrangement, particularly due the forces of inertia of its oscillating masses, i.e., deflecting forces and the damping resistance of its components and the effect of the exterior excitation forces caused by the carrier roller, the apparatus falls into an oscillatory behavior with natural frequencies under special operational conditions, which lead to the fact that the results of the measurements of the apparatus are altered, thus resulting in insufficiently evened up slivers. In addition, in the known apparatus, the initial section of a new sliver is very difficult to introduce between a driving and carrier roller and requires considerable efforts to do so.